GW Leibniz was a late seventeenth-century philosopher, and is often identified as one of the primary rationalist forerunners to Kant; certainly, during Kant's day a century later, Leibniz (as interpreted by Wolff) was the dominant mode of German philosophy. Leibniz is also notable in his own right for holding a number of unique metaphysical positions, not to mention being one of the developers of calculus.
Unlike other philosophers of the early Modern era, Leibniz does not begin (at least, in these two selections) with epistemological considerations; his aim is a system of metaphysics, and he begins with an analysis of the concept of substance. Put positively, Leibniz argues that all substances are 'monads', self-contained, non-interacting metaphysical simples that 'reflect' the cosmos as a whole from their own particular perspective. Thus, when I perceive the tree outside, this is not due to the tree exerting some influence -- direct or indirect -- on me. Rather, this perception is the reflection of the tree within my own essence, and a being that had a complete and precise understanding of the definition of my essence would be able to infer from it that I would have that perception. (This latter is actually the definition of substance Leibniz gives in the Discourse.) The coordination of the perceptions of all these non-interacting simples is guaranteed by God, defined as the most perfect (and thus most powerfull) monad and the only necessary being.
The dense selections also cover several other aspects of Leibniz' thought. In the Discourse, he defends the notion (ridiculed by Voltaire in Candide) that the actual world is the best of all possible worlds, because God has chosen to bring it into existence as the most perfect expression of God's will. The ontological argument is also criticized: Anselm's version shows only that, if God's existence is possible (ie, logically consistent), then God's existence is necessary. The antecedent is argued for in The Monadology. The Monadology also asserts Leibniz' doctrines of the identity of indiscernibles, the principle of contradiction, and the principle of sufficient reason; the PSR is also used to argue for the existence of God, as only a necessary being can provide the sufficient reason explaining the a posteriori fact of the existence of contingent beings.
Locke, selections from An essay concerning human understanding
John Locke would be the paradigm of British Enlightenment philosophy if not for the work of David Hume; still, as Hume was Scottish and Locke English, it would be fair to call Locke the paradigm of English Enlightenment philosophy. Locke was a contemporary of Leibniz, and only half a century or so younger than both Descartes and Hobbes. In this country, Locke is probably best known for his Two treatises on government, which the Declaration of independence clearly references; but our selection is from the equally important Essay.
The Essay is a monumental work, comparable in scope and complexity of content (but not, fortunately, complexity of structure) to Kant's first Critique. The two tomes also overlap in topic and positions defended -- but more on that when we get to Kant. Unlike Kant, who enjoys simply pulling an architectonic out of thin air and imposing it artificially on the subject matter, Locke is quite the taxonomer, and enjoys identifying the natural breaking points and divisions within a topic. This means the reader can sometimes lose the forest of a grand philosophical system for the trees of specific cases; thus, instead of pointing out the most prominent Wegmarken Locke follows, I'll provide a sketch of the entire forest.
The most important single idea in the Essay is that of 'idea' itself. Locke defines an idea as the immediately present contents of one's mind, whether this is as simple as
Locke goes out of his way to distinguish simple ideas -- the phenomenological contents of our minds -- from qualities -- the power subjects have to create those ideas in us. Qualities are divided into primary and secondary. Secondary qualities are things like colour and taste, that vary radically as the subject's interactions with the object change. Primary qualities are, Locke suggests cautiously, probably those mechanists identify as real or essential, and therefore stable: extension, figure, motion. This caution is because mechanism falls short of giving a completely satisfactory account in several ways -- for example, it cannot explain cohesion (why a solid object sticks together as one thing, rather than simply dispersing like a gas) -- but more fundamentally because, Locke argues, we can have no idea corresponding to the underlying causes of our sensations. We have the movie that's playing on the screen, but we aren't allowed to go up and investigate what's behind the hole with the light coming out of it.
A substance is posited as the substratum that binds all these different qualities together. As Locke repeats through the Essay, we have no positive idea of substance whatsoever, whether material or spiritual -- it is simply a je ne sais qua we must suppose exists to explain why these simple qualities always seem to go together. Locke mostly goes along with the mechanists here -- based on our best science, it seems like substances might be organized structures of atoms -- but this is tentative, and cannot explain free will (which, Locke argues, suggests we ought to be dualist about minds), and Locke ultimately adopts a principled agnosticism towards fundamental ontology.
Indeed, Locke's general attitude towards metaphysics is a principled agnosticism or universalism (in the theological sense), driven by his epistemological humility. Essential properties, for example, are cashed out as being matters of the definition of words -- if I am defined as a mammal, then it is an essential property that I have hair; but if I am simply defined as an animal, then this property is no longer essential. Scepticism is dealt with by turning towards the practical: while we cannot have absolutely certain knowledge that our experience of an external, material world is veridical, our judgement that it is so is necessary for us to live our lives and flourish. Thus, rather than wallow in the nihilism that (Locke believes) accompanies scepticism, we should pursue natural philosophy and the empirical investigation of our world, while keeping in mind the humble recognition that this investigation will only suffice for practical judgement, not certain knowledge (and even then, error is inevitable).
Berkeley, Principles of human knowledge, Introduction and s 1-33
George Berkeley was an Irish Bishop early in the eighteenth century and, other than Russell (and possibly Moore), the only philosopher on the reading list to visit the Americas. Berkeley's goal is to radically undermine mechanistic materialism; to this end, at least in the selection, he targets Lockean metaphysics, particularly the primary/secondary qualities distinction. That he has Locke in mind is clear: the first section of the Principles is a parody/homage to Locke's style, and Berkeley cites the Essay two or three times in the few dozen pages.
Berkeley gives three basic 'arguments' against the independent existence of material objects in the selection. The first depends on conflating sensible ideas with sensible objects:
1. Sensible ideas can only exist in the mind.
2. Therefore, sensible objects can only exist in the mind.
The second attacks the primary/secondary quality distinction, and presumes that all of our ideas are particular -- for example, that I cannot have an idea of a generic or general triangle, but instead I imagine some particular triangle to represent any triangle 'indifferently' in a proof. Thus, I cannot have an idea of generic, bare extension without imagining it to have some or another particular colour -- I cannot abstract away the secondary qualities to consider bare matter with only the primary ones. Hence there is no difference between primary and secondary qualities; and since the latter exist only in the mind, so must the former. Berkeley bolsters this point several times with explicitly Lockean relativity arguments.
The third argument is called the 'master argument' by Berkeley scholars, because Berkeley, in the paragraph introducing it, seems to think his idealism can be rejected if its challenge is met. Berkeley says the realist must imagine some absolutely unperceived material object -- say a tree, sitting in a deep forest, with no-one around to see it. The realist might imagine this to be easily accomplished; but, Berkeley points out, the realist is, at that moment, perceiving (thinking of) the tree that is, supposedly, not being perceived. As Downing puts it, "in order to conceive of [unperceived and unthought-of objects], we must ourselves be conceiving, i.e., thinking, of them".
In each case, Berkeley seems to be making the surprising move of identifying the represented (the sensible, material object) with its representation (the idea).
Total pages read: 1498
Interesting philosophical link: more dinosaurs!